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lbhsbz
12-23-2010, 06:11 PM
The more I start measuring and checking their work, the more I'm fed up with automotive machine shops. The latest is a set of Dart aluminum heads for the 496 in my boat...every aspect of the valve job was done at +/- .015...and I suspect all of the valve seats are ground too deep which consequently increases my chamber volume past where I would like it, and I've got a 6cc variation amoungst all 8 chambers, which results in a compression ratio anywhere between 9.8:1 and 10.4:1.

I'm gonna try and fix it. I'm after perfection here. I've ordered up new guides, new seats, and new valves. I've acquired a valve refacer, a valve seat grinding setup, and a guide hone (real one, not once of those ball things). I've got a bore guage in the range of my valve guides (11/32) that will measure to 0.0001". Along with my bore guage, I'll also use a selection of guage pins to verify not only the diameter, but also the straightness of the guides.

I know, seems like I'm spending a lot of money for one valve job, but I do quite a few engines and I anticipate doing considerably more engines over the course of my life, so I might as well tool up to do 'em myself. The initial investment sucks, but I'm hoping it'll pay off.

I'm in the process of building a fixture that will allow me to spin/cant the head on my mill table for the guide honing and seat work.

The seats on these heads are interlocking...which means that after one seat is pressed in, the counterbore for the other valve will have to cut into the first seat slightly. This is where I might need some help. Most of the real machine shops do this with piloted tooling. Piloted tooling for this operation will run me about $1500 to purchase...so I'm not gonna. The plan is to use a boring head with a .750 shank brazed carbide tip boring bar after using a coax indicator on 2 spots of the valve guide, as well as the existing seat to get the head located correctly. I've got a fat and short one for rigidity. The seats are made from Ductile Iron, and the cut for the "interlock" is a section about .040 deep and over about 25 of the 2.5" diam. seat. I've ordered .010" oversized seats becuase I'm doubtful of my abilities to complete an interupted cut without touching the rest of the existing bore. I figure a multimaterial cut will be easier than an interupted cut. This procedure scares me a bit, but with care and light cuts...should turn out well. Minor concentricity issues shouldn't be a problem as I will grind the seats using piloted tooling concentric to the guide. I'm shooting for a .0.005-.007" interference fit.

Any words of advice?

I'll update with pictures as I make headway on this.

cuslog
12-23-2010, 06:28 PM
I can't offer any advice other than: if it were me, I think I'd want to try it on a junk head first.
I'm interested in Cyl. head work on a knee type mill too and will be following your thread with interest.
Hope it works for ya !
Take lots of pictures !

bob308
12-23-2010, 07:41 PM
i got into head work many years ago for the same reason you are now. could not get a good job.

i found that most guides are machined after being installed. which can cause a problem if putting a new guide in. if the valve guide center line is moved even a little bit you have major problems getting a seat with out going too deep. the best way i have found is too relinf the guides that way you are working off the old center line. i use an old walonea set up.

madman
12-23-2010, 07:47 PM
Theres no one around my area good at engine work. I just paid a bunch of cash for a **** valve job at a speed shop in Brantford. The thing was nasty. I have been gathering equipment and anm working on a fixture for holding heads. People just dont take the time to do anything rightn anymore. Thats for sure. You have to almost do everything yourself if you want it done nicely.

RussZHC
12-23-2010, 08:20 PM
Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...

Carld
12-23-2010, 08:36 PM
Ductile iron valve seats in an engine running on unleaded gas? Are you sure you want soft seats?

Whether you use soft seats or hard seats you'll get push off when it cuts into the other seat. Cutting into an aluminum head and part of an iron or hard seat will produce an out of round hole. The reason they use a pilot is to keep the cutter centered.

You better find a scrap head to experiment on because I think your going to find out why you need a piloted cutter.

Doing heads on a Bridgeport type mill works if you have a good fixture to mount the head in that is adjustable in two axis's. It's real important to align the valve guide your working on concentric with the spindle.

The last automotive machine shop I worked at had a level that slipped on a shaft that was a snug fit in the valve guide. Then you leveled the valve guide in two planes. You may want to look into getting one of them.

You can make almost any pilot cutter you need.

Oldbrock
12-23-2010, 08:52 PM
I do a lot of cylinder honing but for valve guide and seat work you need a GOOD automotive machinist with the latest equipment. I send anything like this to Ken McDonell in Stettler Alberta. The only guy I know who can turn out a perfect job. It just isn't worth the hassle of trying to set up a head with no suitable mounting surface and having to do it multiple times in a mill. This guy builds race engines as well as regular run of the mill engines and knows his stuff. Trying to find someone who takes pride in their work can sometimes be frustrating. There has to be a reputable engine shop somewhere in your area, ask the racing fraternity, they'll know. Peter

JoeFin
12-23-2010, 09:16 PM
Piloted tooling for this operation will run me about $1500 to purchase...so I'm not gonna.

Top of the line - $800

You need to correct for the slightest angular misalignment. That is the reason for the piloted tooling.

But yes it is quite a bit of money especially considering once you purchase all that "Head Rebuilding Tooling" your gonna want a "Flow Bench" to go with it

PixMan
12-23-2010, 09:26 PM
Having been to J&M Machine (Southborough MA) and seen the machinery they have and their mastery of it, I wouldn't even attempt to do it myself. And I've been a machinist for over 30 years.

John and Mike (brothers) have the latest in the specialized machine tools and tooling, can cast their own babbit bearings (using a variety of compounds) and do impeccable work.

I'm not saying you can't do it or shouldn't try, I'm just saying I know of at least one shop that is top-notch and carries a great reputation to back it up. And there's knowledge of the motors, tools, materials and methods that 30+ years of doing nothing but that kind of work has benefited them, and left me "knowing what I don't know."

http://www.jandm-machine.com/

BTW, the fact that you'd be using a brazed carbide boring bar right off tells me that you may not be any more successful than the shop that didn't do a good job. This a job for quality tooling, and that ain't it.

P.S. - .005" to .007" isn't a press fit, it's a "not a chance" fit.

lbhsbz
12-23-2010, 09:35 PM
Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...

I kinda screwed up.....maybe not. I was looking at seat cutting setups, that use a single carbide blade to cut all 2-3-4-5-6- whatever angles at once...and that was somewhere in the neighborhood of $1500 realistically. That's will multiple toolholders so I could leave each one setup so everything would be dead nuts the same on all the seats. The "base" package is about $750. Instead, I bought a seat grinder setup, but you can't use this to cut the counterbores with any level of accuracy.

I'm not sure what you're asking about the overlap thing....please elaborate and I'll try to answer. You may have touched upon something I haven't thought of...but I don't really understand your question.

lbhsbz
12-23-2010, 09:37 PM
I do a lot of cylinder honing but for valve guide and seat work you need a GOOD automotive machinist with the latest equipment. I send anything like this to Ken McDonell in Stettler Alberta. The only guy I know who can turn out a perfect job. It just isn't worth the hassle of trying to set up a head with no suitable mounting surface and having to do it multiple times in a mill. This guy builds race engines as well as regular run of the mill engines and knows his stuff. Trying to find someone who takes pride in their work can sometimes be frustrating. There has to be a reputable engine shop somewhere in your area, ask the racing fraternity, they'll know. Peter

I'll spend more money trying everyone in the state to find someone who cares than I will to tool up and do it myself. Every machine shop in the world comes well recommended by those that like shiney surfaces but don't disassemble and measure to check their work after delivery. Plus, the kind of job I'm looking for is $$$. Most shops simply won't do it.

Tim Clarke
12-23-2010, 09:42 PM
It would seem that engine rebuilding is rapidly becoming a lost art. When I was in the trade, there were 3 local automotive machine shops that were good to excellent, and 3 that weren't. Now, 30 years later, they're mostly gone. The place I worked was as good as any, offering the run of the mill stuff, plus balancing, align boring, and driveline service. Lots of good guys worked there. Picky, knowledgeable guys. I learned a lot from them. I left because I couldn't see any future in it. Turns out it was a good move, but now the company I work for won't rebuild any engines or gearboxes in-house. There's still plenty of other work to keep us busy, but who wants to replace king pins when there's engines needing rebuilding?

I would suspect that in many cases the reason that people find it hard to get the quality of work they want, is because the good men who are skilled and knowledgeable enough to the required work have moved to greener pastures. In my case it was a long time ago, and it was for the money. Like 35% more and double the benefits. Last time I knew, it was more like 50% nowdays. That is comparing auto machinists to diesel mechanics. Other trades may be similar, I don't know.

Last summer my daughter's Escort spit up an intake seat and I considered fixing it here. The proscess seemed pretty involved for 4 seats and a valve job, so I farmed it out to the last local shop here I'd trust. Cost, if I remember correctly was about 150 bucks. 4 seats, 4 cyl valve job, and the laundry. They did a nice job. I wonder how those guys keep bread on the table.

When I was rebuilding engines for our fleet at work, I used to send blocks to B and G in Seattle. They do first class work on things that count. The biggest engine we have is the smallest they work on. Perhaps that's the secret, find a shop that does first class diesel work, and see if they do any gas or race stuff?

TC

mike4
12-23-2010, 09:46 PM
Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...
I dont see what fitting guides and seats has to do with the timing , all of the range of engines that I have either had work done on by others or have completed myself the only timing was done by the camshaft and its associated parts.
Just curious, not doubting anyones knowledge.

Michael

lbhsbz
12-23-2010, 09:47 PM
Ductile iron valve seats in an engine running on unleaded gas? Are you sure you want soft seats?

Whether you use soft seats or hard seats you'll get push off when it cuts into the other seat. Cutting into an aluminum head and part of an iron or hard seat will produce an out of round hole. The reason they use a pilot is to keep the cutter centered.

You better find a scrap head to experiment on because I think your going to find out why you need a piloted cutter.

Doing heads on a Bridgeport type mill works if you have a good fixture to mount the head in that is adjustable in two axis's. It's real important to align the valve guide your working on concentric with the spindle.

The last automotive machine shop I worked at had a level that slipped on a shaft that was a snug fit in the valve guide. Then you leveled the valve guide in two planes. You may want to look into getting one of them.

You can make almost any pilot cutter you need.

Ductile Iron is what the Dart assembles their heads with, and I haven't heard of any issues with them. I'm sure there are better parts out there, but I just called up Dart and ordered everything from them. Prices were decent, and I'm getting stuff that I know will work with their heads.

I agree with you about cutting this with non-piloted tooling. It may be impossible. My fixture is ridgid. It consists of a 2" wide 8x10" block on each side with a 3.5" hole bored in each piece. I made 2 pieces of a 4" long piece of roundstock that will fit and clamped into the holes in the blocks (blocks have a slit and bolt to pinch the bore around the round stock)...Then a piece of 1" thick x 3" x 24" material that will bolt between the roundstock "spindles" and bolt to the intake or exhaust surface. The mounting holes in the big crosspiece are slotted to give me the 4 of cant that I need to hit the intakes. I'll use some kickstands off of the other side of the head to brace it to the table. Should be pretty stout.

lbhsbz
12-23-2010, 09:51 PM
Top of the line - $800

You need to correct for the slightest angular misalignment. That is the reason for the piloted tooling.

But yes it is quite a bit of money especially considering once you purchase all that "Head Rebuilding Tooling" your gonna want a "Flow Bench" to go with it

Where? I'm dealing with 2.460 OD intake seats....most don't even make cutters that big....so that puts me into the adjustble cutters which are big bucks.

I'm seriously considering reselling my valve grinding setup and nutting up for the ball drive setup...then I can cut seat counterbores with the addition of a $30 blade. I hadn't thought of counterboring for the seats when I made the decision to buy the grinder setup for $300.

Maybe I'll throw a chunk of iron into a block of aluminum and try to bore a hole threw it....for the amusement if for nothing else....I kinda know what'll happen.

JoeFin
12-23-2010, 10:32 PM
Where? I'm dealing with 2.460 OD intake seats....most don't even make cutters that big....so that puts me into the adjustble cutters which are big bucks.

Goodson

http://www.goodson.com/store/product_images/3D_Banner.jpg

and here are all the counter boring attachments too

http://www.goodson.com/store/template/product_display.php?NID=132&SID=588ec370bd000cd9c34eb837aadf3a9a

and here are all the bowl profiling attachments

http://www.goodson.com/store/template/product_display.php?NID=113&SID=588ec370bd000cd9c34eb837aadf3a9a

Of course you would need a good sized mill, make your own roll over jig, and probably use a few practice heads before you rip into those Dart heads

PixMan
12-23-2010, 10:51 PM
I'll spend more money trying everyone in the state to find someone who cares than I will to tool up and do it myself. Every machine shop in the world comes well recommended by those that like shiney surfaces but don't disassemble and measure to check their work after delivery. Plus, the kind of job I'm looking for is $$$. Most shops simply won't do it.

The shop I posted about certainly stands behind their work. They do motors for everything from Ferrari's to Model T's, and stand behind their work. They are doing motors for the best-known restorers out there, and ship all over the world. I know I saw a straight 8 in there from a 1928 Mack, right next to an original Ford 427 cu in side oiler from a true Shelby Cobra.

The photos of the machines in their shop are not up-to-date. They've added a new boring machine and a new Sunnen hone that just blows me away.

lbhsbz
12-23-2010, 11:34 PM
Goodson

http://www.goodson.com/store/product_images/3D_Banner.jpg

and here are all the counter boring attachments too

http://www.goodson.com/store/template/product_display.php?NID=132&SID=588ec370bd000cd9c34eb837aadf3a9a

and here are all the bowl profiling attachments

http://www.goodson.com/store/template/product_display.php?NID=113&SID=588ec370bd000cd9c34eb837aadf3a9a

Of course you would need a good sized mill, make your own roll over jig, and probably use a few practice heads before you rip into those Dart heads

Yep....that's what I've been looking at. $850ish for the"starter kit", then $200 for a ball driver, and another few hundred for extra toolholders, carbide pilots at $100+ each, and a few extra bits....$1500 to get setup. Looks like that might be the road I go down. I can make money reselling the grinder setup I bought.

v860rich
12-24-2010, 12:00 AM
I'd be interested in seeing your fixture for mounting heads on BP.

THANX RICH

People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!!!

Willy
12-24-2010, 01:43 AM
Not much help here, but seeing as it's almost Christmas perhaps if you've been real nice this last year maybe Santa will bring you one of these.:D

http://www.newen.com/assets/PDF/EPOC%20Brochure%20ENGLISH.pdf

From the same site Dart BBC valve seat:

http://www.newen.com/Pages/Vids/dartin.html

Lots more videos and equipment there to drool over.

RussZHC
12-24-2010, 02:05 AM
I maybe the one :o :confused: ...the point I was trying to make about the amount the valves physically overlap and timing was that if there ever, ever is something in the valve train that is not up to being that precise (I have something like valve "float" in mind...one weaker spring or even an angle that is not precise, or a rocker arm whose ratio is off just a smidge) the fact that there is overlap makes contact more likely than when there is no physical overlap, doesn't it?

I had a BB that had oversize (but not that big) and very little in terms of clearance between the top of the piston and the valve so warning was given by the head guy it would be chancy so I just thought overlapping of valves made something similar possible...I am not saying it should not or is not done (way too out of the loop these days), just saying.

Just thinking about it...would that be the degrees between/overlap exhaust and intake at various parts of the complete cycle? And if that thought is correct, is there even enough flexibility/adjustment in the cam you intend to use...like I said been a long time and I may have this completely wrong...I just have some idea of the costs involved and I never was even using Dart heads, race motors are not particularly known for longevity as it is AND if this is headed for the street, then I think there are whole other issues.

strokersix
12-24-2010, 07:33 AM
A word of encouragement. I've done a little bit of this kind of work on turret mills without proper tooling and yes, it can be done. Investment in tooling and fixturing will certainly help.

Careless mechanic home shop - failure
Careless mechanic pro equipment - maybe OK maybe not
Careful machinist home shop - might take a while but good results
Careful machinist pro equipment - well this is obviously the best

Sounds like you have the careful machinist part. Now you just have to decide the trade-off between tooling investment and how much time you wish to spend.

I don't have any 3 angle cutters, still use grinding stones. I'd like to upgrade at some point so I'm watching this thread.

A.K. Boomer
12-24-2010, 08:23 AM
Just briefly,,, Im with Carld about the ductile iron, if your going through all this trouble then why would you put the equivalent of valve seat pot metal back in?

Go with stellite - its designed for no-lead.

Also - .007" sounds like too much of a press fit.



I would research the interference cut into the valve seat, I believe I would cut into the intake seat due to it not having to deal with the heat factor, just thought it worth mentioning as there might be potential for the exhaust to distort once heated to operating temp, What does the factory do? (just curious)

Also -- IMO there's no need to order special seat bore cutting equip. if you have your act together machining wise,
Here's what to do --- just use a boring head and keep it about .005" under the seat bore size, then move the cutter from center into the direction of the already installed seat and hog out the overlap material till it matches the bores tolerance -- this way you will not hit the original head material while gaining clearance - the minor circular deviation at the interference intersection will not make any difference with a good press fit.

Willy
12-24-2010, 09:56 AM
While I certainly don't consider myself "pro" when it comes to hi-perf. valve jobs, since it has been a while since I've done this and I too may be out of the loop.
But I do remember doing lots of valve seat installations in both aluminum and cast iron and I know from past experience that .005-.007 is not out of the ball park for valves of the size that the OP is installing in an aluminum head, especially a ductile iron seat.

Here is a link to a manufacture of hi-perf. valve train components that actually specifies an .008 interference fit for it's ductile iron seats:
http://www.cheprecision.com/html/install2.html

And another recommendation for .007:
http://www.enginebuildermag.com/Article/1946/valve_seat_installation_procedures.aspx

Be that as it may, personally ductile iron would not be my first choice for seat material either.

A.K. Boomer
12-24-2010, 10:15 AM
I get concerned with galling material out in aluminum when the press becomes too extreme so I go with the minimum - but that's just me and im no expert either,

If the material gets "plowed" then you can not only end up with the seat not seating down all the way (or cocked) but you can actually reduce the press fit.
I just looked up a few references and they do state .007 to .008 for ductile iron in aluminum but for stellite in aluminum they state .006".
A handy tool for pressing in seats is to cut an old valve head off (make damn sure its not a sodium filled exhaust valve:eek: ) and stab it into a pre-machined chunk of steel that matches the seat perfectly and has a "receptor" on the other end for an air hammer punch bit,,, slick as snot - esp. after heating the head up on your chimenia:p

cuslog
12-24-2010, 11:47 AM
I've posted this here before, maybe you've seen it, maybe not.
Some of the guys here are race engine pro's and using knee mills to do cyl. head work. Lots of good info here.
http://www.speedtalk.com/forum/viewtopic.php?f=1&t=21647&hilit=Bridgeport+valve+job
Do a search on that site for "bridgeport valve job" or similar, theres lots of other threads about it too.
You'll find guys there selling the rollover fixtures and tooling as well.
Trouble is; it ain't cheap !

JoeFin
12-24-2010, 01:00 PM
and of course you'll need this link to go along with the link above

http://www.flowbenchtech.com/plans.html

lbhsbz
12-24-2010, 01:36 PM
I've posted this here before, maybe you've seen it, maybe not.
Some of the guys here are race engine pro's and using knee mills to do cyl. head work. Lots of good info here.
http://www.speedtalk.com/forum/viewtopic.php?f=1&t=21647&hilit=Bridgeport+valve+job
Do a search on that site for "bridgeport valve job" or similar, theres lots of other threads about it too.
You'll find guys there selling the rollover fixtures and tooling as well.
Trouble is; it ain't cheap !

Yup. I've spent the last 2 months doing a lot of reading there. I've even talked to a few of the guys on the phone. It's a wealth of information.

brucepts
12-24-2010, 07:43 PM
and of course you'll need this link to go along with the link above

http://www.flowbenchtech.com/plans.html

Ah . . . that would be me :)

BillK
12-24-2010, 09:20 PM
ibh,

Take it from someone who does this for a living, you really need to find a junk head to practice on before you ruin your nice Darts.

First of all, if you have a .015" difference in valve depths, that is not what is causing your variation in chamber volumes. If you sink a 2.250" intake valve .015" you pick up a little less than 1 cc. The chambers on the Dart heads are not machined as accurately as you would like to believe, I would not be a bit surprised to find a 8cc difference from chamber to chamber on thier heads when new. You are not going to pickup 6cc by redoing the seats :(

Personally, If I was asked to repair your heads, I would simply equalize all of the valve installed hgts by machining the existing seats. Then I would cc the chambers and "massage" the small ones until they were all the same. Then If you wanted to decrease the chamber volume, you can machine the deck surfaces to get whatever size you want.

I personally think you are making a big mistake in wanting to replace all of the seats. If you do, make sure you understand the correct interference fit, and prepare to use your oven to heat the head and a freezer to chill the seats before you install them. Probably would be a good idea to have a pneumatic seat driver, makes it a lot easier than doing them by hand. You really need a piloted driver to install the seats. Cannot imagine doing it any other way.

Have you measures the valve lengths ? I have seen them vary .005" to .010" brand new. That can account for some of your hgt difference. I try to get seats within .005" when I do them, but most customers are not willing to pay the price for the time it takes to do so :(

Also, if you plan on getting the single blade type three angle cutters, make sure you have a way to sharpen them. They will usually only do one head before needing a touch up sharpening.

If you have any questions, I dont mind an e-mail or PM.

BillK
12-24-2010, 09:26 PM
This is what you need :)
http://www.newen.com/

lbhsbz
12-25-2010, 10:41 PM
Thanks Bill. I'll call em on monday and see if they can match the price I paid for my 30 year old Sioux setup. :-)

lbhsbz
01-06-2011, 02:10 AM
The tooling is coming together....got the sioux seat grinder setup on Monday....and I'm a bit disappointed. After some inspection, the 10 pilots that came with it are all worn out...supposed to be .385 to fit in the stoneholder and most are in the .381-.382 range. Also, all of the stoneholder bearings are shot. I ordered new stones and holders and those showed up today....along with my ball drive tooling

I also got a Fowler seat Concentricity Gage (bought it new) and it doesn't impress me either....it's got at least a couple thou clearance on a new .385 carbide pilot, which kind of defeats the purpose of the gauge itself being accurate to .001. I've got to call them in the morning and see if they can do any better than that. Elsewise
I'll return it and use my coax indicator to Gage seat to guide Concentricity.

http://img.photobucket.com/albums/v201/machschnelGTI/35436308.jpg

http://img.photobucket.com/albums/v201/machschnelGTI/29c58bf8.jpg

I got the replacement belt from mcmaster for my valve grinder...but even with the Tg collet setup, I'm having trouble holding better than .0025 TIR...so I've gotta play with that bit.

http://img.photobucket.com/albums/v201/machschnelGTI/f0147b07.jpg

Got started on the flow bench over the weekend....hope to finish it this weekend

http://img.photobucket.com/albums/v201/machschnelGTI/4c171d17.jpg

And my sunnen valve guide hone showed up too

I'm not to thrilled with the taped pilot idea either....seems all that's available is tapered orexpanding, neither of which do a real good job at keeping things concentric. My goal is to hold the guide dimension within .0002, and the pilots are tapered .002" over 2". On BBC heads, The seats are pretty far away from the guide, so the the tapered pilots will have a .003" or so error near the seat. I'm going to talk to some grinders tomorrow about making some carbide pilots that only taper .0003-.0004 over the length of the guide.

I think I may be going a bit overboard with this....lol

davidwdyer
01-06-2011, 03:14 AM
Judging by the empty "containers" on the bench, it looks like something is flowing. :)

hardtail
01-06-2011, 07:38 AM
Gasoline is for washin parts, alcohols for drinkin and nitros for racin..........

tdkkart
01-06-2011, 09:53 AM
The tooling is coming together....got the sioux seat grinder setup on Monday....and I'm a bit disappointed. After some inspection, the 10 pilots that came with it are all worn out...supposed to be .385 to fit in the stoneholder and most are in the .381-.382 range. Also, all of the stoneholder bearings are shot. I ordered new stones and holders and those showed up today....along with my ball drive tooling

I also got a Fowler seat Concentricity Gage (bought it new) and it doesn't impress me either....it's got at least a couple thou clearance on a new .385 carbide pilot, which kind of defeats the purpose of the gauge itself being accurate to .001. I've got to call them in the morning and see if they can do any better than that. Elsewise
I'll return it and use my coax indicator to Gage seat to guide Concentricity.

I got the replacement belt from mcmaster for my valve grinder...but even with the Tg collet setup, I'm having trouble holding better than .0025 TIR...so I've gotta play with that bit.

I'm not to thrilled with the taped pilot idea either....seems all that's available is tapered orexpanding, neither of which do a real good job at keeping things concentric. My goal is to hold the guide dimension within .0002, and the pilots are tapered .002" over 2". On BBC heads, The seats are pretty far away from the guide, so the the tapered pilots will have a .003" or so error near the seat. I'm going to talk to some grinders tomorrow about making some carbide pilots that only taper .0003-.0004 over the length of the guide.

I think I may be going a bit overboard with this....lol


I think you may be finding out just how slob-ovian automotive machine work is. Some of the stuff that I've seen that's "perfectly acceptable" is just obscene. Supposed, and actually well regarded, race engine shops that do horrible work.

I've seen numerous blown-up stock car engnes, more often caused by piss poor machine work, or sloppy assembly work, than sub-standard parts. Saw one that nearly 1/2 of the rod bolt nuts were in the oil pan undamaged. The shop wouldn't stand behind it.

A few years ago I sent a set of Harley twin cam cylinders and pistons to a very well regarded shop for boring and honing. The cylinders were supposed to be fitted to the individual pistons. Specified piston clearance was .0010-.0012" per the manufacturer.
When the cylinders returned, the pistons would not slide through the bores at all. Got hold of a set of torque plates so I could do a proper job of measuring the bores.
How can you claim a clearance of .001"-.0012" when there's .003-.004" taper in the final bore size?? The bores were actually undersized by as much as .002", or over by .002" depending on where you measured........WTF??

I called up the owner of the shop and explained the situation. 2 days later I had a new pair of cylinders in hand, worked on personally by the shop owner, that were perfect.

JoeFin
01-06-2011, 10:48 AM
http://img.photobucket.com/albums/v201/machschnelGTI/f0147b07.jpg

Got started on the flow bench over the weekend....hope to finish it this weekend

http://img.photobucket.com/albums/v201/machschnelGTI/4c171d17.jpg


Really very impressed you jumped into the Flow Bench immediately. I think you'll resolve more of your problems on the Flow Bench then any where else.

As for the rest of your tooling - Never buy used pilots on Ebonner or any where else and measure the pilots you have after each set of heads you use them on.

I have an old Kwik-Way valve grinder myself. Check the Ball Bearings in the chuck for any pitting or rust spots. I probably have a few extra 1/2" precision ball bearings around here from when I replaced mine. Once you have the Valve Grinder all dial in you'll be surprised by the number of "Factory Ground Valves" you find Non-Concentric.

You also might want to check out some of the New Special Purpose Type Grinding Wheels for it as well. The newer valve materials machine quite differently then the older stuff.

Below is a photo @ x30 checking the results of grinding. Some of the newer materials will gouge when ground with the wrong type of stone

http://i198.photobucket.com/albums/aa83/Freakindj/Valve-2001-1.jpg

and I can not stress enough - some practice heads

BTW: here is a picture of my old Kwik-Way - when I first got it it had a .002 run out in the chuck from rust pitting on the Ball Bearings. In the photo it has an ordinary collet chuck (I drilled out the back side so the valve could fully insert) in the valve chuck so I can grand valves with less the .250" stems

http://i198.photobucket.com/albums/aa83/Freakindj/Valve-2003.jpg

lbhsbz
01-06-2011, 11:02 AM
Judging by the empty "containers" on the bench, it looks like something is flowing. :)
Yep.....after scratching my head and doing math for an hour trying to figure out what angle to set the inclines Mano at such that it will compensate for my res. Surface area and tube diameter while indicating a four to one ratio using an inch scale......I started drinking beer to see if that would help me get it right. I'm down to a total error of .034" wc over 24"....which bugs me. I can't figure out the answer because trig says you cant make a right triangle the way I need to make it......I think. I dunno, I'm lost at this point. We'll figure out. I'm gonna try rum and coke this weekend to see if that helps...lol.

saltmine
01-06-2011, 11:11 AM
Gad, that takes me back. I learned to grind valve seats and reface valves on my Dad's Kwik-Way valve grinding machine. Of course, his was in much better shape, having bought it new. Yes, it was quite common to have the pilots wear out, and they could be bought at most well equipped auto parts stores. A lot of bad valve jobs came out of the shops because of management and greed. Management wanted everything done right now,(Time is money) and didn't want to pay to keep the machines in good working order. Many mechanics learned to operate the machines by watching experienced guys use the machines, and striking out on their own, to make more money...Formal training was pretty scarce. I started out as a kid in an auto parts store machine shop. The machinist was a perfectionist, and he didn't want his reputation tarnished by shoddy work, so I learned how to do the work properly. My proudest moment came when he took a two-week vacation and told our boss that I could handle anything that came in while he was gone.

Gradually, cylinder head reconditioning was something you sent out to a specialty shop, and the 'ol valve grinding machine sat quietly, rusting. Occasionally somebody would turn it on to sharpen a chisel or grind the edge off of something...99% of today's present crop of "technicians" don't know the first thing about reconditioning or repairing cylinder heads, or cylinders.
Everything is "farmed out" or replaced with new. Many times I've seen a guy install old used valves into a brand new cylinder head without even cleaning them up or checking them...with predictable results. Another "lost art" that's rapidly disappearing.

Michael Moore
01-06-2011, 01:07 PM
Bill Jones has a lot of interesting shop-built head fixtures and tooling

http://ryanbrownracing.com/Bill_Jones_Photo_Gallery.html

I just spent a fair chunk of change on some Neway and AV&V tools for a small vintage roadracer (5mm stem) project. I've got my cylinder fixture for the FlowQuik done and some cans of port molding compound, and yesterday I spent some time modeling the valves/guides/etc assys. It must be that time of year. :)

Bruce's flowbench site is great, but SpeedTalk gets a lot more traffic from a wider range of people.

cheers,
Michael

lbhsbz
01-24-2011, 06:08 PM
Well, I finally found some time to get my cylinder head fixture built...used a couple sets of Shars angle plates, an old 327 crankshaft, a couple chunks of aluminum, and a piece of 5/8x2.5" steel stock. It's kinda clumsy but once you get it where you want it it stays there. I'll work on some threaded adjusters some day.


http://img.photobucket.com/albums/v201/machschnelGTI/c8d851b5.jpg

This is a junk practice head that I'll be further destroying.


I'm still trying to figure out the resurfacing thing....hard to do with a 22" long workpiece and only 25" of table travel...I've got some ideas...a pretty slick one actually...that involves making the head move 35" with only 15" of table travel, but I've got some more work to do before I'm ready to tell anyone about it and get laughed at.

strokersix
01-24-2011, 07:04 PM
I decked this 28 inch long inline block on my 8x36 mill. Used 17 inches of table travel to cover the area. Tram was dead nuts. Can't feel the witness mark nor pick up any error with my 24 inch straight edge so I'm pleased. Not a production setup for sure but got it done.

http://i965.photobucket.com/albums/ae131/strokersix/DSCN3802.jpg

http://i965.photobucket.com/albums/ae131/strokersix/DSCN3803.jpg

http://i965.photobucket.com/albums/ae131/strokersix/DSCN3801.jpg

lbhsbz
01-24-2011, 07:13 PM
I was thinking of building a bracket that clamps onto the knee dovetails on the main casting of the machine. The bracket will include a 2 inch vertical pivot pin. Then I'll need a piece of tooling plate that I have rest on the mill table and pivot off of this pin, such that the plate can travel in an arc and slide over the table. I'll drive the plate using a slotted hole about 1/3 of the way between the pivot and the center of the workpiece with an arm that hangs off of the backside of the mill table....so that for every 1" of table movement, I should have about 3" of travel on the workpiece through it's arc....so I need about 35" of workpiece travel, which should be about 12" of table travel. I'll have some springloaded rollers holding the sliding plate down the mill table and I'll oil everything up real good before I assemble it to reduce wear on the mill table. I don't think it would get enough use for either component to see any real wear. It'd be slicker than $hit I think....if it works.

strokersix
01-24-2011, 07:59 PM
I understand your idea and it seems possible. One issue you should consider if you haven't already is how much mass will be hanging off the table at the extremes.

I think that is one reason for my recent success. I made sure the tram was dead nuts and only used 17 inches of table travel so the block and table were not hanging off the end.

lbhsbz
01-24-2011, 08:08 PM
If I do it right, there won't be any mass hanging off the table.

If the table remained stationary and centered throughout the whole thing, the workpiece would be hanging 2.5" of off one end of the table....then give another 7 or so inches for the fixture, lets call it 10".

If I run the table through 20 inches of it's travel (I said 12" earlier without having done any actual math) to move the fixture 31" (22" long head plus a 9" face mill)...the fixture may overhang 1/2" at each extreme.

Edit: Plus, I'm dealing mainly with aluminum heads..which weigh about 35lbs. The iron head in the picture is a small block head that's not that heavy, and it's just to play with the seats on. I hate cast iron BBC heads, they're too damn heavy.

lbhsbz
02-19-2011, 08:05 PM
I cleaned the place up a little bit and started re-measuring everything and putting together a spreadsheet so I knew exactly what I had to do. I found that I made a mistake last time I measured stuff up....I did each head at a different time. This time, I didn't zero my gauges between the two heads...and I found something that explained a lot of questions. On one of the heads, the exhaust seats were cut 0.062 -0.085" deeper than on the other head.....There's that 4cc of chamber volume I've been looking for. Guess I've gotta put new seats now.

I've been at kind of a standstill because I was having trouble measuring the valve guides. I was attempting to measure them using 3 different methods...to kinda check my work, and all 3 gave me different readings.

I have chinese small hole bore gauge that reads 0.0001...I was having a lot of trouble getting consistant results with this....I took it apart and deburred the mechanism (it was pretty bad), which improved it considerably, but I still didn't know if I could trust it.

I also tried to indicate the amount of play in the valve, then do some trig to calculate the clearance.

I also have those super badass carbide pilots that I had ground such that each had only a 0.0003" taper over 3 inches, and I have the ranges marked on them. I planned to use these like go-no go gauges.

I picked up a holtest (inside hole mic) and a mitutoyo bore gauge, and rechecked everything....according to the mitutoyo bore gauge, which agreed with my holtest, my bore was .3430, but the .3425-.3428 pilot would only slide in about 1/3 of the way into the valve guide.

I started measuring the pilots every 1/2" and found that while the ends hit my number, there is larger diameter in the middle...This particular pilot starts out at .3425, then tapers to .03432 in about an inch and a half, then back down to .3428. Guess I've gotta go see the tool grinder on Monday and ask him what happened.

Regardless, I've got come up with a trustworthy method of measuring the guides.

I removed the rest of the seats...welded old valves into them and knocked them out from the stem side. None of my larger bore gauges are able to measure a hole that's only .375 deep because the mechanism is to large, so I made a bunch of aluminum gauges in incriments of 0.001. Not the best way, but I'm not sure of another one. I don't trust myself with telescoping gauges.

RussZHC
02-19-2011, 11:31 PM
What dimension are you aiming for with these guides?

I was going to suggest KISS but damn, if it is .3430, its right between all drill and reamer blanks

11/32 is .3438
"R" is .3390
.850 is .3346 and 9.00 is .3543
the bonus would be reamers are often +.0002 to 0 and drills from
0 to -.0003 so nearly a made "go-no-go" gage.

Would something in some pin gage be nearer...but those are most often listed as 2" in length which I doubt will be long enough for the entire guide...your custom ground gages maybe the only choice...?

Curious, what is the valve stem diameter?

lbhsbz
02-20-2011, 01:49 AM
Valve stem size is .3415". I'm shooting for .0015 clearance on the intakes and .0018-.002 on the exhaust.....so, .3430 and .3435" guide diameter. I've got a sunnen honall to size the guides......but I was getting confused because the pilots, which I had ground special, didn't fit......never thought to measure it in the middle. I need the pilots to fit the guide somewhat I can keep seat Concentricity under control.....I've got a steel expanding pilot, but it's nowhere as rigid as my carbides.

On the Brite side, I measured up the seats I pulled out, and with the exception of the exhaust seats in one head, they're the same height as the new ones. The 4 bad ones are about .060 shorter, but...with where the angles are cut, I can still grind it shorter and keep the valves about .120" higher in the chamber. I made a couple mandrels on the lathe to reduce the diameter of the oversized seats to fit the existing counterbores....hopefully I can get the new seats in tomorrow.

greybeard
02-20-2011, 02:59 PM
lbhsbz,

Something else to consider... core shift in the combustion chambers.

Recently I did a set of Big Chief heads and for giggles and grins, here's what I did and what I found:

I slid an Intake valve into the exhaust guides. On some cylinders, the Int. valve would go down into the chamber close to the Exh. seat before touching the casting. In other cylinders, the Int. valve would catch on the deck and not go into the chamber at all. (The chambers were cast and not fully machined.)

Oh yeah, the Int. side appeared to have about the same clearance between the wall and the valve head though. I do suspect that the chambers were significantly different due to the core shift.

I'm not sure how that affected the cc volume, as I was hired to find out why the valve guides were a problem, and did not actually cc the heads.

The heads were sent back to the OEM for new guides and seats.

BTW, the guide problem (bent guides) was caused by bead blasting with the guides left in the heads. This allowed the blast beads to 'pack in' behind the guide, between the guide and the long side radius, thus bending the guides approx. .010 to .018 along the full length of each guide (banana shaped). Imagine where these beads would go after startup!

My 2 cents...
Greybeard

johnd
02-25-2011, 10:04 PM
I was one of those Slobovian automotive machinist's for 20 years but I've been out of it for the last 20. I'm curious to know what condition your heads were in when you took them in? There is no reason the shop would purposely sink the seats that much deeper in one head if it wasn't needed to clean them up. Especially if they are using grinding equipment. I'm wondering if they were possibly using a 3 angle cutter (like you are considering buying) on their seat / guide machine? Certain heads / seats / cutter combinations have a tendency to chatter and they may have tried too long and hard before giving up and going back to grinding to get it right. Shame on THEM if so!
Concerning solid tapered pilots--- Most of the part that fits in the guide is straight. There is a taper on the upper inch or so to seat tight in guide. To be properly equipped you need several of them for each basic stem size. Sioux or Goodson will list 5-6 pilots ranging from about .340" to .345" for the 11/32 guides you are working with. Pick the largest one that fits your guide with the taper seated. These are maybe a little more accurate than an expansion pilot and more rigid for certain. I don't know how brittle your "badass" carbide pilots are but I have visions of them snapping off when your cutter comes around and hits that intake seat (assuming you end up using piloted tooling)or when you are driving your seats in.
Concerning leveling the head--- Someone mentioned the spirit level assembly that slips on the pilot and I think you should get one or rig one up. Piece of cake for a machinist. Flip it end to end to verify accuracy and of course figure a way to verify your mill is sitting dead level with spindle perfectly square. That slob automotive machinist has one that fits not only his pilots, but also in the spindle of his machine, and he will check & level the cylinder head for each and every guide if needed. They are not necessarily all exactly the same. Take a good look at the fine adjust tilt features on his fixture and you can see how he can do this in a few seconds. He also has an air float table that centers cutter spindle in the guide in seconds. You need your coax indicator for centering once you have it level and I can see that working ok BUT, leveling your head by comparing coax readings at 3 places in the guide & seat and adjusting your fixture to get them all the same sounds like an exercise in futility to me.
Concerning replacing guides--- If I remember you are installing new guides also. I've never worked on Dart heads and I don't know if they have the same setup as original cast iron BB heads with guides going through water jacket & 2 different ODs. Your new guides will answer this for you.
Concerning Sunnen guide hone vs reamers--- The typical Sioux, Kwik-Way, or whatever, reamer has a pilot section and will do a nice job if carefully fed with a self aligning hand drill and if it's not worn out. The Sunnen hone is nice to have in an emergency but slow, cumbersome, and requires way to much progress measurement to get 16 guides right. I suggest you practice on your junk head to get your stroking down just right or you will end up with bell mouthed guides. I'd stick with reamers if possible.
Counterboring for new seats--- Sounds like you are turning your new .010" over seats back to standard, or as needed, to fit your existing counterbores. With the heat, expansion. and contraction an exhaust valve sees I wouldn't ASSUME your existing bores are perfect. I would wait till you have the intake seats installed and the overlap section machined out of the exhaust counterbore before trimming those exhaust seats down. If you end up using valve guide piloted tooling I don't know how you will pull that off! I like the idea someone had of using your boring head shifted a few thousandths towards the intake seat and taking very light cuts out of the overlap piece until it just matches up with your existing counterbore.
Valve seats--- If Dart says the seats they send are good enough I believe them. I started in the engine shops in the mid 70s when unleaded gas came in and there was a mad rush to install hard exhaust seats in everything. We did see the occasional case of the plain integral cast iron seats giving out, in certain engines, IF they were worked really hard. The vast majority survived fine with plain cast iron and I'm sure the Dart seats are a better grade. You certainly don't need Stellite seats. WHATEVER you end up with, just be sure to radius or deburr the corners before you drive them in so you don't shave aluminum from counterbores. I would agree with the folks saying .007" or .008" press fit. The general rules for press fits (I think) assume a solid shaft pressing into a solid chunk of iron and would call for MUCH less. A valve seat ring into an aluminum head is a different story. If you end up with a bit of counterbore you can peen over the edge of the seat I say do it. It might help flow, eliminate a hot spot, and possibly help retain a seat if it ever should work loose. I'm with the camp that says metal to metal contact for heat transfer is a better situation than
using loctite for retaining seats, some may argue that point. Maybe there is a better product that takes the heat, I don't know. In any case, if done right, they will not fall out.
Best of luck! I really want to hear how it turns out. And don't give up on all automotive machinists. Some are very good, some, not so good. It's a different situation than manufacturing. A completely rebuilt engine may not have more than .010" removed from anything and the total amount of metal removed is just a few ounces. Con-rod & main bearing bores get machined and end up at the SAME size. And, you can't simply toss every 35th part coming off the line because it's out of spec.
ALSO--- To Greybeard, Were those heads with bent guides GLASS bead blasted, or STEEL SHOT blasted? Glass beads certainly will not bend a valve guide .010" to .018" and nobody in their right mind would remove a set of valve guides to bead blast a head and then re-install them. Even if steel shot blasted. And, how did you slide those valves into those banana shaped guides anyhow? My 2 cents....

lbhsbz
02-25-2011, 11:46 PM
Thanks for the reply.

The valve job was done on a serdi machine....and I don't care if it chattered or why the seats were all cut to different depths. The fact of the matter is than if the existing seats couldn't be used to do it right, new seats should have been installed. There's no excuse for a "performance"'job to end up the way mine did.

As far as the seats, I ended up using the existing counterbore. They were i'n good shape and measured up fine once I got my tooling in order. I used a .006-.007 interference. The overlap only existed on the upper .080 of the counterbore, so I very carefully cleaned it up with a fine stone on a dremel....there was hardly any material to remove. I made some piloted drivers to knock the seats in.

The guides are actually a bit on the tight side. I trust my mitutoyo bore gauge and it's much more repeatable. I did a little work on the guides and got the intakes to .0013-.0016, and set the exhausts at .0018-.0020"....and they're straight.

I got the pilots back from the grinder yesterday and I'm not sure how he did it, but he straightened them out. Carbide pilots seem to fairly common these days, and the old Souix style mostly straight with a "lock" taper at the very top are a thing of the past.....aside from having straight carbide pilots in .0001" increments, I think I've got the next best thing. At about $200 each for the pilots, it was an investment that will hopefully pay off with near perfect Concentricity.

I'll be doing the job with 3 angle ball drive tooling, but have to first do some research to select the right profiles.

sdeering
02-26-2011, 12:08 AM
FYI I have the same kwickway valve grinder. My valve chuck would not hold the valve true so the holder was cut off and a new collet system made up to go in its place. Now it hold the valve dead nuts.

Not sure why you are fretting about the guides so much with measuring. You can pretty much tell the amount of wear by pulling the valve out 1/2 inch and giving it a wiggle. Compare it to a new guide and valve. If you don't like the fit push the old guide out, push a new one in and ream or as some of the newer stuff push the correct size ball through the guide to re-size done.
Most of the older manuals had a speck for the valve wiggle. You probly know the guides will wear at the ends more than the middle.
The builder of the heads should be able to point you in the right direction for guides and tooling size.

Good on you to do this your self.
Most of the shops in Central Alberta have closed the doors as well. I have been seeing lots of engine equipment for sale lately. Good thing I have no time for motor making nowadays.

lbhsbz
10-05-2011, 01:34 PM
Figured I post an update to this.

I had to abandon the project...the realization that I was gonna spend way to much money and as many hours in doing this finally set in...I realized that my tooling was not up to par, and couldn't justify another $5K investment for something that I'd probably only use a few times. I ended up selling all the parts, the boat, some of the tooling that I'd aquired that still needed some more love before it was really usable, and because summer had arrived, picked up a tunnel hull with a 200hp 2 stroke mercury on it to go play with at the river. When the $$ situation improves, I might dive back into it.

gary350
10-05-2011, 03:44 PM
That is why have the local SPEED SHOP do all my engine work. They are a bit more expensive but their work is 100% correct every time. Leave off the exhaust valve rubber seals this gives those HOT valves more lubrication and they will last longer. The engine will burn a very small amount of oil maybe 1/4 of a quart between oil changed but its not a problem and it will save your heads and valves.

http://home.earthlink.net/~gary350/mytruck.jpg

The 1967 chevy truck has a 350 engine with headers and 2.5" dual exhaust open exhaust system. The carburator is Edlebrock 600 cfm 4 barrel and aluminum intake. The cam is 262/270 Extreme Energy by CompCams. Stock lifters, crank, pistons and rods. The heads have 1.95 valves. The smaller 1.95 valves gives it more low end torque than the 2.02 valves. The heads have been ported, milled, and CCd to give the engine exactly 9.0 compression ratio on all 8 cylinders so it will run good on pump gas. It has a 400 turbo automatic transmission with a shift kit. The distributor has a rpm kit in it. The timing is set at 12 deg at 600 RPM's and advances to 32 degrees at 2500 RPM's. The truck appear to have been lowered but it has not. The tire diameter is 2" less than stock and 14" wide which gives it the appearance of being lowered. From a dead stop I can punch the gas to the floor and the wheels will peal for about 30 feet then stick like glue. The truck will go like lighting to 40 mph and shift to second and peal the wheels some more. Passing gear shifts at 4500 rpm in warm weather and 4000 rpm in cold weather. The cams torque range is 1500 rpm to 4500 rpm. The stall converter is stock 1800 rpm. I have 2 home made mufflers that are so quite you almost can't hear the engine run.

Its a lot of fun to be the first vehicle in the RIGHT lane parked at a RED light waiting for it to turn GREEN and have some teen age kid in a hot rod car or a Red Neck pull up next to me and try to use the turning lane as the passing lane. I hate people that refuse to take their place the back of the line and try to use the turning lane to pass everyone. Surprise, surprise, no one gets around me unless I let them pass. lol. fun, fun, fun. :-)

Jasper1990
11-05-2011, 08:22 PM
I have been machining racing engines for 20 years. I have read over a large part of the threads and your concerns are in the right direction as far as your guide clearances are concerned. However you should be performing your valve job with as little clearnace as possible realitive to the valve stem. If you are sealed at no clearance then you can rest assured that you will be able to run very tight stem clearance and not sieze up.
The valve seat profiles are very important in reguards to air flow. The biggest gains and losses are made at the seat angle and back cut angles. Change them by a 1/2 a minute and airflow changes drastically. I have some custom seat profiles that will make very good airflow and I can set seat depths with in .001" realitive to the deck surface of the head.
Changing out valve guides on any after market aluminum cyl head is a last resort. The guides that all the major AM head builders use have poor concentricty to begin with. Once they cut the seat and get to the bowl area of the casting with the valve job that's it. Bowl diameters are very sensative to air flow also. Poke a guide out that just slightly off and push in one thats perfectly straight and your only option is a larger head dia. valve to correct bowl concentricty.
Three angle valve jobs on any of these heads is a mistake. Takes 4-5 angles depending on lift on the intake side. Takes a radius shaped valve job and bowl on the exhaust.
You should be doing a valve job at .0003" using carbibe pilots that are as tight as you can run and allow them to slightly broach and straighten out the frac in the guide and then lap the valve to the seat and make sure its sealed at no clearance. In a boat application that uses lake water to cool you can run as little as .0006" clearance on the intake and .0012" exhaust. If you run CB seats its a must. By running tighter clearances you are able to cool the valve much better and your valve job will last for years and years of major abuse. There are many other advantages of tightening your guide clearances. You just have to make sure you are sealed up at near zero clearance.
Not all automotive machinists are hacks. Most of them are too full of pride to learn a better way of doing it. I have tried my best to stay on the R&D side and keep learning. Have built several world champion offshore racing engines and NHRA SC racing engines.
I have a Serdi equiped machine shop and I use sunnen diamond guide hones. I also use PCD for machining my deck surfaces on aluminum cylinder heads. I can also do custom port work.
Anytime anyone needs help with any machine work on their engine your more than welcome to hold my feet to the fire. I will do my best to answer any questions anyone has. Yall have a nice day!